The remains of Khaled al-Assaad, a Syrian archaeologist beheaded by ISIS militants, have yet to be recovered, his son told AFP on Wednesday. The official SANA news agency reported in February that authorities had uncovered three corpses in Kahloul, 10 kilometres (six miles) east of the ancient city of Palmyra where Assaad was killed in 2015. Assaad was believed to be among them, SANA said at the time, ahead of DNA testing. But two months later, DNA results have shown that the remains of the archaeologist have yet to be found, his son Tareq said. "Authorities have just informed us that the DNA test results are not compatible with my father," he said. "Our sorrows and wounds have returned," he said. "We had hoped to close this wound." Assaad, known as "the father of Palmyra", was 82 when ISIS militants executed him on August 18, 2015, three months after they overran the so-called "Pearl of the Desert". Seen as a pioneer of Syrian archaeology, Assaad was director of antiquities in Palmyra for 40 years until 2003. He was responsible for the discovery of several ancient cemeteries and oversaw the excavation of 1,000 columns as well as the sites stunning necropolis of 500 tombs.